1. Field of the Invention
The present invention is broadly concerned with food delivery systems designed to maintain food at a selected temperature over relatively long periods of time. More particularly, the invention pertains to such food delivery systems which include a magnetically heatable thermal storage device within a food-holding container, wherein the storage device may be selectively heated within said container by an induction charging station. In preferred forms, the charging station indefinitely maintains the selectively heated portion of the thermal storage device at a user-selected regulation temperature by using contact-less feedback from said device.
2. Description of Prior Art
The problems associated with the delivery of hot foods to consumers has in recent years taken on greater significance owing to the growth in convenience foods and those delivered directly to households. Although the rise in pizza deliveries is a prime example, other foods are now commonly delivered to the door, from simple hot sandwiches to complete meals.
For instance, most prior art pizza delivery systems consist simply of a partially insulated, non-sealing vinyl bag or sometimes a well-insulated nylon bag into which one or more cardboard boxes containing pizzas are placed so as to maintain the pizzas as warm as possible during delivery to the customer. Although the sauce layer of a freshly cooked pizza is typically over 200 F., the sauce layer upon delivery is often as low as 110 F., particularly where delivery times in excess of 30 minutes are experienced.
The problem of cold-delivered pizzas is only partly due to inefficient delivery bags and the like. In a typical pizza operation, once a pizza emerges from the oven it is removed and placed upon a cutting table to be sliced. The pizza is then placed in a cardboard box. Very commonly, two or more pizzas are to be delivered to the same address and multiple pizza bags full of pizzas are delivered to several different customers on the same delivery run. Under these circumstances, the boxed pizzas are placed under infrared heating lamps until all pizzas for a given run have been prepared, sliced and boxed. Due to the logistics involved in such operations, some pizzas can be almost cold before the delivery run even commences.
In 1998, Dominos Pizza introduced the Heat Wave.TM. pizza delivery system. This consists of an insulated nylon pizza bag, a wax-filled resistively heated plastic-coated thermal storage disk, and a rack charging system into which up to 20 thermal storage disks can be plugged so as to charge them with thermal energy. This system has several drawbacks. The thermal storage disks are heavy, weighing in excess of three pounds. Thus, the delivery container is no longer lightweight once the disk is in place. Furthermore, the disk requires a substantial time to become fully charged with thermal energy, taking over two hours from room temperature and over thirty minutes after a typical delivery to be fully charged. Additionally, the thermal storage disks must be plugged into and out of the charging rack, thus requiring the operator to perform additional steps. Finally, to implement the rack charging system, a typical pizza parlor must be substantially modified in terms of its power supply network and floor space to accommodate the rack.
There is accordingly a need in the art for an improved food storage and delivery system which will permit the purveyor to maintain the food products at or near a desired temperature over sustained periods, while also allowing delivery under conditions to substantially maintain this temperature. An effective hot food storage and delivery system thus requires a lightweight delivery container, a fast-charging thermal storage device capable of storing and efficiently releasing large amounts of thermal energy, and easy to operate equipment not requiring skilled labor.